There are known in the prior art covered buttons in which a piece of material is assembled over a button shell and is held in place thereover by a back with which the shell is assembled. The back may be of any type known to the art which carries any suitable fastening element such as a wire eye, or a plastic hook, or any other type of fastener which permits it to be assembled in position. There are known in the art, moreover, hand-operated, semi-automatic and completely automatic machines for assembling such buttons.
One industry in which such covered buttons find wide application is the upholstery industry, wherein the material which is used as the button covering is of the same material as is the upholstery covering which may be fabric, leather, or the like. In the upholstery industry, while a relatively large number of the same size covered buttons may be run off at the same time, only a relatively few of the buttons will require the same covering material at a particular time because of the wide range of cover fabric usually offered by the manufacturer. The material used in the course of assembling one run of buttons all of the same size may range from single ply thin goods, such as cotton, silk, rayon, or the like, up to medium or heavier weight materials, such for example as heavy knits, velvets, vinyls, and so forth. A third grade of material which may be used would be very heavy suede and thick leathers and backed vinyls. Dies for handling these various grades of material in the art are known as "LU" dies for light upholstery, "HU" dies for medium weight materials, "HUX" dies for heavy materials, and "HUXX" dies for extremely heavy materials. The dies may be so marked or may be color coded to differentiate between the different fabric weights. It will readily be apparent that, in the prior art, to make satisfactory covered buttons for the full range of materials, the manufacturer must stock several sets of dies for each size of button and must change dies each time the grade of material changes.
The difficulty in the prior art is that the average size manufacturer does not wish to go to the expense of having more than one set of dies and, particularly, does not wish to expend the time and energy required for changing of dies when going from one weight of material to another weight. Where the user attempts to use only one die for all of the various grades of material which are used in the course of a run of a single size button, the resultant buttons may be unsatisfactory. Either the buttons may pop apart or the force exerted in assembling the button is so great that the button back or shell, or both, are crushed in the course of the assembly operation, or otherwise faulty buttons are produced.